Database Concepts

Objectives

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• the concept of a database and relational database. • diff erent components of the database. • types of database models. • types of relationship. • the concepts of relational algebra

Summary

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• DBMS is a computer based record keeping system • Data is unprocessed data which contains any character, text, word or number has no meaning • Information is processed data, organized and formatted. • Examples of RDBMS are mysql, oracle, sql server, ibm db2 • Redundancy means duplication of data in a database. • Data Consistency means that data values are the same at all instances of a database • Data Integrity is security from unauthorized users • Table is known a relation • A row is called a tuple • A column is known as an attribute • Types of data model are Hierarchical, Relational, Network, ER and Object model. • Hierarchical model is a simple tree like structure form with one-to-one relationship called parent-child relationship • Relational Model represents data as relations or tables • Network model is similar to Hierarchical model but it allows a record to have more than one parent • ER model consists of entities, attributes and relationships "• Object model stores data as objects, attributes, methods, classes and inheritance • Normalization reduces data redundancy and improves data integrity • Different types of Relationship are one-to-one, one-to-many, many-to-one and many-to-many relationships • Database Normalization was proposed by Dr.Edgar F Codd • Relational Algebra is used for modeling data stored in relational databases and for defining queries on it."